The present invention relates to a method and to a system for recovering carbon dioxide from raw gas obtained by gasifying fossil fuels such as coal and petroleum, i.e., from gasification gas.
Combined cycle power generation has been implemented in which gasification gas is combusted to drive a gas turbine, and also in which steam is generated from the combustion exhaust gas to drive a steam turbine. The combustion exhaust gas, which is released to the atmosphere, contains carbon dioxide. From the viewpoint of global environmental protection, performing carbon dioxide capture and storage (CCS) is highly desired.
In this connection, as shown in FIG. 5, the following has been proposed in Japanese Patent Application Publication No. 2006-522004. Specifically, raw gas produced in a gasifier 110 is subjected to dust removal by a scrubber 120. Then, CO contained in the raw gas is reacted with steam 3 in a CO shift reactor 130 to perform a shift reaction, which produces CO2 and H2 (CO+H2O→CO2+H2). H2S and CO2 contained in this CO shifted gas are then removed one after another by a physical absorption process called the Selexol process, or more specifically, by a H2S absorption apparatus 140 and a CO2 recovery apparatus 150. Then the CO shifted gas is supplied to a gas turbine.